A keratome is an instrument used in ophthalmic surgery and, more importantly, in surgery to reshape the cornea for vision correction. A keratome incises a generally spherical segment of the cornea except for a connecting hinge. The cornea segment is lifted and held aside while the exposed truncated cornea surface is shaped for vision correction. Thereafter, the spherical cornea segment is repositioned to cover the shaped, truncated cornea surface. The cornea segment heals to the shaped surface, resulting in a reshaped cornea that acts as a corrective lens.
It will be appreciated that a keratome must achieve an accurately positioned, surgically precise cut with minimal tissue damage to enhance the healing process. Further, the cut must remain uncontaminated, also to aid the healing process and avoid irritation and infection.
In accurately positioning and performing a cornea cut, it is known to use a suction ring as an interface with the eye. Suction is used to temporarily secure the suction ring to the eye in a desired position. Typically, a suction ring is secured to the sclera, near the periphery of and surrounding the cornea.
It is also desirable to measure the cornea and coordinate the extent of the incision with the size of cornea in order to remove a properly sized cornea segment and to provide an appropriate hinge in conjunction with the excised cornea segment.
It is also known to apply a cutting instrument with the suction ring. Thus, the suction ring positions and presents the cutting instrument with respect to the cornea. Clearly, if any slippage or disengagement of the suction ring occurs, a correspondingly inaccurate cut may also occur. Present suction rings occasionally do experience slippage or disengagement, and it is believed this occurs because of a poor interface with the surface of the sclera resulting in loss of suction or uneven suction along various segments of the ring. Currently, engagement of a cutting instrument with a suction ring is often difficult to achieve, because the engagement must be precise, making the engagement difficult to initiate.
Precision of the cornea cut requires proper positioning of a cutting instrument with respect to the cornea, which is achieved by the location and secure attachment of the suction ring, and also requires a very smooth operating cutting blade. Cutting instruments often use a reciprocating cutting blade to achieve a smooth, precise incision. Any flutter in the operation of the reciprocating cutting blade can cause a somewhat ragged incision, with consequent difficulties in replacing the cornea segment and smooth healing thereof.
The cornea cut must also remain uncontaminated, because any foreign matter in the incision may become encapsulated and cause irritation and possible infection. Cutting instrument designs which support a cutting blade on a bearing surface adjacent the area of the incision increase the risk of contamination. Contact between the cutting blade and the bearing surface creates friction and wear. This not only heats the cutting blade, but also sloughs off microscopic metal wear particles. These may lodge in the cornea incision, with undesirable effect.
It is also desirable to translate the cutting instrument across the cornea in a smooth manner and to reliably stop the translation of the cutting instrument at the furthest extent of the cut. Non-damaging withdrawal of cutting instrument is also desirable.
There is also a need to quickly and easily load blades into the cutting instrument, and to remove blades after use.
Therefore, there is a need for a keratome including a suction ring that easily, accurately and securely positions a cutting instrument with respect to the cornea and that provides a surgically precise, uncontaminated incision of a cornea segment. There is an additional need for improved automation in making the incision.